You are climbing a stair case. It takes n steps to reach to the top. Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top? 跳台阶,之前写过递归的,这次写个非递归的. 到第n层的方式 其实就是 到第n-1层的方式(爬一层)和到第n-2层的方式(爬两层)的和 class Solution {…

题目简述: You are climbing a stair case. It takes n steps to reach to the top. Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top? 解题思路: 这个是最简单的动态规划问题,我们考虑爬上n阶有几种情况?既然只能一次走一步或者是两步,那么要到第n阶的种数要不然是从第n-1阶走一步上去,要不然…

You are climbing a stair case. It takes n steps to reach to the top. Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top? 思路: 最简单的DP问题:递归+查表 代码: int climbStairs(int n) { vector<, -);//忘了在memo[0]没有意义的时候,数组初始…

Follow up for "Unique Paths": Now consider if some obstacles are added to the grids. How many unique paths would there be? An obstacle and empty space is marked as 1 and 0 respectively in the grid. For example, There is one obstacle in the middl…

Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below. For example, given the following triangle [ [], [,4], [6,,7], [4,,8,3] ] The minimum path sum from top to bottom is 11 (i.e.,…

Implement strStr(). Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack. 思路: 注意,在for循环中条件有计算得到的负数时, 一定要把计算括起来转换为int, 否则会默认转换为uchar 负数就会被误认为是一个很大的数字. ; i < - ); ++i) 实现很常规: int strStr(string haystac…

Given a non-negative number represented as an array of digits, plus one to the number. The digits are stored such that the most significant digit is at the head of the list. 分析:思路是很清晰的,就是从数字最低位开始向上循环,如果是9就变成0,如果不是就直接当前位加1,返回.如果全都是9,就在最高位加一个1. 但是我写C++…

题目:就是判断已有的数字是否冲突无效,若无效返回flase 有效返回true 不要求sudo可解 用了char型的数字,并且空格用‘.'来表示的. 思路:只要分别判断横向 竖向 3*3小块中的数字是否有重复或者无效就可以了  就是单纯的麻烦 不难 #include<iostream> #include<vector> using namespace std; class Solution { public: bool isValidSudoku(vector<vector&l…

Given an array of integers, find two numbers such that they add up to a specific target number. The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2. Please note that…

Given an array of size n, find the majority element. The majority element is the element that appears more than ⌊ n/2 ⌋ times. You may assume that the array is non-empty and the majority element always exist in the array. 思路: 找主要元素,用major记录主要字母,n记录ma…